Watch List notes:

ROMAN AND BYZANTINE COINS

Trajan Decius, 249-251. Heavy Antoninianus (Silver, 24mm, 8.33g 6), Rome. IMP C M Q TRAIANVS DECIVS AVG Radiate and cuirassed bust of Trajan Decius to right. Rev. GENIVS EXERCITVS ILLVRICIANI Genius standing left, holding patera in his right hand and cornucopiae with his left; to right, legionary standard. Cohen 49 and RIC 16c (both referring to normal weight issues). Very rare. Well centered but lightly struck. Rough surfaces and some peck marks, otherwise, very fine.

Curiously heavy antoniniani are known for the emperors of the mid 3rd century but they are very uncommon and they have had differing interpretations. They may be test strikes that escaped into circulation (though they are not invariably well struck as one would expect); they could simply be mistakes, which were struck on heavy flans that escaped the eyes of mint inspectors; or they could have been intended to be higher value presentation pieces (not very likely since they looked exactly like normal coins). In any case it is clear that the ancient user was unfamiliar with what this coin was supposed to be: the presence of what are termed "peck marks" on the obverse edge shows that someone wanted to test to see if the coin was actually silver (such marks are well known from medieval coins).